Apparatus for controlling electrode oscillation

ABSTRACT

A welding apparatus wherein the welding electrode is moved transversely in oscillating motion across the weld path, the electrode to be capable of dwelling at either the fore or aft point of maximum displacement of the transverse movement path, the voltage between the electrode and the workpiece is automatically maintained constant by means of an automatic voltage control mechanism.

United States Patent [191 Kazlauskas et a1.

[ Dec.4, 1973 APPARATUS FOR CONTROLLING ELECTRODE OSCILLATION [75]Inventors: Gasparas Kazlauskas, North Hollywood; Kennison L. Vowel],Canoga Park, both of Calif.

[73] Assignee: Astro-Arc Co., Sun Valley, Calif.

[22] Filed: Feb. 22, 1972 [21] Appl. No.: 227,886

[52] US. Cl. 219/125 R, 219/60 R, 219/76, 219/137 [51] Int. Cl B23k 9/12[58] Field of Search 219/125 R, 125 PL, 219/76, 60 R, 60 A, 61,137

[56] References Cited UNITED STATES PATENTS 3,230,341 Blackburn 219/125R 3,646,309 2/1972 Smith et a1... 219/125 PL 3,005,901 10/1961 King219/125 R 3,619,552 11/1971 Gordon 219/125 R 3,621,183 11/1971Chamb0nnet.... 219/125 PL 3,135,857 6/1964 Von Voros 219/125 PL PrimaryExaminerR. F. Staubly Assistant ExaminerL. A. Schutzman Attorney-RobertE. Geauque [57 ABSTRACT A welding apparatus wherein the weldingelectrode is moved transversely in oscillating motion across the weldpath, the electrode to be capable of dwelling at either the fore or aftpoint of maximum displacement of the transverse movement path, thevoltage between the electrode and the workpiece is automaticallymaintained constant by means of an automatic voltage control mechanism.

19 Claims, 17 Drawing Figures Pmminni 41w 7 3.777. 115

SHEET 5 BF 6 ll: TIMER 258 i D Y /284 304 I80 *25 CLUTCH 284-\ v 278 j:::i. r A v :28O

T TIMER K-R CIRCUIT CLUTCH BACKGROUND OF THE INVENTION The field of thisinvention relates to the welding of separate metallic cylindricaltubular elements by the gas shielded tungsten electro-arc weldingprocess. More particularly, this invention relates to welding apparatuswhich produces efficiently an extremely strong weld. This inventioncontemplates an apparatus which employs automatic gas tungstenarc-welding along a circumferential path in tubular structures.

Within recent years there have been commercially available structures toautomatically weld together separate sections of pipe. These structuresare required to compensate for the problem of the welding of the largerdiametered workpieces. These structures effect the welding operationautomatically, it only being necessary to locate the pipe sectionswithin the welding apparatus and initiating the welding procedure.

However, the structures of the prior art have included certain inherentdeficiencies. The weld bead produced may frequently be a half an inch ormore in width. A welding electrode which moves in a straight line toproduce the weld bead results with the weld bead being quite high in thecenter and not filled in at the sides of the weld. Therefore, in orderto avoid this, it is desirable to have the welding electrode oscillatetransversely across the weld bead'as the welding electrode moveslongitudinally.

It has further been found that even with transverse oscillation of thewelding electrode, the produced weld bead still tends to be high in thecenter and not filled in at the edges. This occurs especially ininstances of welding of the larger diametered work pieces. Prior to theapparatus of this invention, it is believed that there is no knownapparatus to overcome this deficiency.

Another important feature of automatic welding apparatuses is that thewelding voltage be maintained substantially constant in order to producea strong weld over the entire length of the weld bead. However, undernormal circumstances, as the electrode moves over the workpiece, thedistance of the .electrode from the workpiece will vary. The arc voltageis a direct function of the distance of the electrode from theworkpiece.

Previously there have been attempts at designing automatic voltagecontrol apparatuses to be employed in combination with automatic pipewelding structures. However, previously the automatic voltage controlapparatuses effect movement of the welding electrode at relatively slowspeeds, typically 5 to inches per minute. As a result, except when theelectrode moves quite slowly, the automatic voltage control system isnot capable of responding instantaneously to are voltage changes. Inother words, there may exist an undesirably long interval between changein arc voltage and attempts at correction. It is desirable to producethe weld as fast as possible and for this reason the electrode normallymoves at several feet per minute. Therefore, within the prior art theautomatic voltage control systems are not capable of responding quicklyenough to maintain a preset gap between the electrode and the workpiece.The end result is a weld which is poor in quality and may readily break.

SUMMARY OF THE INVENTION The welding electrode within this invention isconnected to a support means which is pivotally mounted to the weldingapparatus housing. An actuating arm is pivotally mounted with respect tothe support means with the free end of the arm rotationally secured toan external gear. The external gear is in continuous engagement with aninternal gear. A drive means is to be connected to the external gear andis to effect rotation of the external gear about the internal gear. As aresult of the external gear moving about the internal gear, asubstantially linear movement of the actuating arm is produced whichresults in a slightly arcuate movement of the welding electrode byreason of the support means being pivoted back and forth in anoscillatory motion. The internal gear is supported within a housing andis capable of manual pivotal movement in respect thereto. By manuallypivoting the internal gear, the relationship between the internal gearand the external gear changes. This relationship can vary from nooscillation of the welding electrode to a point of maximum oscillatingdisplacement of the welding electrode. This amount of oscillation is tobe preestablished prior to welding in view of the size of the weld beadto be produced.

The motor which is employed to drive the external gear also effectsrotation of an idler gear. The idler gear is the same size as theexternal gear and makes one complete revolution in the same time that ittakes for the external gear to make one complete revolution. The idlergear includes a pair of diametrically spaced apart apertures with theapertures being located at different radial spacing with respect to eachother. A light source is to be located on one side of the disc with afirst and second photocell located on the opposite side of the disc. Thefirst photocell is to be lined up with one of the apertures so that uponthe idler gear making a complete revolution, light from the light sourcewill pass through one of the apertures into contact with the firstphotocell. The second photocell is located so that in a similar mannerthe light from the light source will pass through the other of theapertures and into contact with the second photocell. The arrangement ofthe apertures is such that the light from the light source will passthrough the first photocell with the welding electrode located at oneend of its transverse path movement and the second photocell will beactivated when the electrode is at the opposite side of the transversemovement path. Upon either photocell being activated, the driving motoris disengaged from the driving of the external gear for a period oftime. This period of time may be selected to run for a few tenths of asecond or a few seconds. After the desired time of dwell has occurred,the motor is automatically reengaged thereby continuing the oscillatorymovement of the welding electrode.

The automatic voltage control apparatus included within this inventionemploys the use of a torque motor to effect extremely quick movement ofthe welding electrode toward and away from the workpiece. To stop themotor instantaneously and prevent the motor from running inertially, abraking circuit is employed about the motor to immediately short circuitthe motor upon being disengaged. The voltage between the weldingelectrode and the workpiece is constantly being measured and istransmitted to a comparison type of apparatus. Within the comparator thesensed voltage is compared with the reference voltage and an errorvoltage, either positively or negatively, is ascertained. This errorvoltage, if it exceeds a deadband voltage, is transmitted to effectdriving of the motor either clockwise or counterclockwise, as desired,to cause extremely quick movement of the welding electrodeeither towardand away from the workpiece. Since the distance the electrode is fromthe workpiece directly effects the arc voltage, the arc voltage istherefore controlled and is to be maintained at a substantially presetconstant value. Additionally, a safety device is employed within theautomatic voltage control apparatus of this invention wherein if theworkpiece was removed and displaced a substantial distance from thewelding electrode, it would be possible with prior art devices to strikethe arc of the welding electrode. This could be very undesirable aspotential injury could'occur or damage to other structures. Therefore,if the workpiece is removed, a potential occurs between an electronicsground and the welding arc ground. This potential results in operationof a transistor which in turn operates a relay which opens the circuitto the welding electrode. Therefore, it is not possible to initiate thewelding operation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the weldingapparatus of this invention showing the welding apparatus in operationto join together separate segments of a pipe type of workpiece;

FIG. 2 is a front view of the apparatus shown in FIG. 1 taken along line22 of FIG. 1;

FIG. 3 is a cross-sectional view of the apparatus of this inventiontaken along line 3-3 of FIG. 1;

FIG. 4 is a cross-sectional view of the apparatus of this inventiontaken along line 4-4 of FIG. 2;

FIG. 5 is a view of a portion of the apparatus of this invention takenalong 5-5 of FIG. 2;

FIG. 6 is a cross-sectional view through a portion of the apparatus ofthis invention taken along line 66 of FIG. 5;

FIG. 7 is aview similar to FIG. 6 but showing the light sourcecommunicating with the opposite photocell which is shown in FIG. 6;

FIG. 8 is an exploded isometric view of the mechanism included withinthis invention to effect the oscillatory movement of the weldingelectrode;

FIGS. 9 to 14 are schematic views showing different positions of theoscillatory motion apparatus within'this invention to effect a differentamount of oscillating motion of the welding electrode;

FIG. 15 is a block diagram of the electrical circuitry employed toeffect production of the dwell within the oscillating motion;

FIG. 16 is an electrical circuit diagram of the block diagram shown inFIG. 15; and

FIG. 17 is an electrical circuit diagram of the automatic voltagecontrol system employed within this invention.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENTS Referring particularly tothe drawings, there is shown in FIG. 1 the welding head apparatus 20 ofthis invention which includes basically an apparatus housing 22, afiller wire feeding mechanism 24, and an electrode housing 26. Thewelding head apparatus 20 is to provide for welding of a firstcylindrical tube 28 to a second cylindrical tube 30 by the gas tungstenarc-welding process. The welding head apparatus 20 is to produce awelding be'ad 32 to result in the integral connection between the firstcylindrical tube 28 and the second cylindrical tube 30. It is envisionedthat the cylindrical tubes 28 and 30 are to be of enlarged diameters inwhat is commonly termed pipes. Although the apparatus of this inventionhas been found to be particularly applicable to the welding of enlargeddiameter structures, it is to be considered within the scope of thisinvention to employ the apparatus of this invention in other weldingenvironments such as welding smaller diametered structures.

Within the electrode housing is supported a welding electrode 34.Flexible conduits 36 are to supply within the electrode housing 26 theelectrical energy to the electrode 34 and also an inert gas to beconducted about the electrode 34 to the welding area. The internalcomponents of the electrode housing 26 forms no direct part of thisinvention and therefore need not be described here in detail. Theelements thereof are considered to be conventional and well known in thefield. Additionally, the electrical energy to the electrode 34 as wellas the inert gas is deemed to be supplied from conventional sources andalso need not be described here in detail. It is to be noted that theelectrode 34 is basically what is termed a non-consumable electrode andwill normally be formed of a tungsten material.

A filler wire 38 is to be supplied to the welding area by means of thefeeding mechanism 24. The feeding of the filler wire 38 is to beautomatically accomplished by means of a control mechanism, not shown.The wire 38 is conducted from a spool, not shown, about idler pulley 40and in between the rollers 42 and 44. The rollers 42 and 44, as well asthe pulley 40, are rotatably supported upon the support plate 46. Thesupport plate 46 is fixedly secured to motor housing 48. The motorhousing 48 includes a motor, not shown, which is used to employ thedrive pulley 50. The drive pulley 50 cooperates with an idler pulley 52.The filler wire 38 is to be frictionally bound between the drive pulley50 and the idler pulley 52 which, upon rotation of the drive pulley 50,effects longitudinal movement of the filler wire38. The motor within themotor housing 48 is to be automatically controlled so that the end ofthe filler wire 38 is maintained directly adjacent the welding area.

Secured by a screw type of fastening means to'the apparatus housing 22is a cover 54. Thefunction of the cover 54 is to protect the movingcomponents located within the apparatus housing 22. Located within thecover 54 is an opening 56. The opening 56 is provided to permit theshaft nut 58 to pass therethrough. The shaft nut 58 is fixed upon shaft60. A gear 62 is fixed upon the shaft 60 directly adjacent the nut 58. Abelt 64 cooperates with the gear 62 with the other end of the belt 64being connected to a drive gear 66. The drive gear 66 is fixedly securedupon motor shaft 68 of the motor 70. The motor 70 is fixedly locatedwithin the apparatus housing 22 by means, not shown.

The motor 70 is to be activated from a source, not shown, and is toeffect rotation of the motor shaft 68 and the drive gear 66. Thisrotational movement is transferred by means of the belt 64 to the gear62. It is to be noted that the motor 70 is capable of being rotatedeither clockwise or counterclockwise. Upon the gear 62 being rotated,the shaft 60 is rotated either counterclockwise or clockwise.

The shaft 60 is rotatably supported by hearing assemblies 72 and 74which are fixed within the apparatus housing 22. The shaft 60 includes aseries of screw threads 76 which are in continuous engagement with athreaded block 78. The threaded block 78 is fixedly secured to the outerrace 80 of a bearing assembly 82. The inner race 84 of the bearingassembly 82 is fixed to a guide block 86.

Also fixed within the guide block 86 is a longitudinal bearing assembly88. The bearing assembly 88 provides low frictional retention of theguide block 86 upon guide rod 90. The guide rod 90 is rotationallysupported by means of bearing assemblies 92 and 94 with respect to theapparatus housing 22. The guiderod 90 is prevented from longitudinalmovement with respect to the apparatus housing 22 by means of snap ring96 located at one end of the rod 90 with a nut 98 located at theopposite end. 5

Upon rotation of the shaft 60, the nut 78 is caused to movelongitudinally either upward or downward'upon the threaded portion 76 ofthe shaft 60. Rotation of the nut 78 itself is prevented due to beinconnected through the bearing assembly 82 to the guide block 86.Surrounding the shaft 60 on each side of the nut 78 and being connectedto the apparatus housing 22 are flexible bellows 100 and 102. It is thefunction of the bellows 100 and 102 to prevent foreign matter fromcoming into contact with the shaft 60 and prevent smooth unhinderedmovement of the nut 78 upon the shaft 60.

As the nut 78 is moved upon shaft 60, it can be readily seen that theguide block 86 moves in synchronism therewith longitudinally upon theguide rod 90. A connecting arm 104 is secured by a fastener 106 to theguide block 86 and also moves in synchronism therewith. The connectingarm 104 is fixedly secured to the electrode housing 26. Therefore, asthe guide block 86 moves upon the guide rod 90, the electrode 34 eithermoves toward or away from the workpiece which is represented by thecylindrical tubes 28 and 30.

It is to be noted that the welding voltage is directly dependent uponthe distance of the electrode 34 from the workpiece. It is desired thatthis welding voltage be maintained in a preselected level. However, eachworkpiece is slightly different in shape and inherently includesrecesses and raised areas. Therefore, the gap between the electrode andthe workpiece, after being initially established, cannot be maintainedconstant as the electrode moves about the workpiece. It is to beunderstood that normally the welding apparatus will be moved about theworkpiece. However, it is envisioned that the workpiece could be movedrelative to the apparatus. An appropriate type of movement apparatus toeffect movement of the welding apparatus 20 of this invention about theworkpiece isreadily shown and described within U. S. Pat. applicationSer. No. 136,112, filed Apr. 21, 1971, entitled Welding Head SupportingApparatus.

Because the gap between the electrode 34 and the workpiece 30 cannot bepreestablished and maintained, some type of control apparatus must beemployed which will automatically adjust the gap between the electrode34 and the workpiece as the apparatus moves about the workpiece. Such acontrol system is shown within FIG. 17 of the drawings.

It is highly desirable to keep the welding voltage as constant aspossible in order for a high quality type of weld to be produced. Sincethe welding apparatus is designed to move at the rate of several feetper minute about the workpiece, the electrode 34 will quickly come uponany hiatus formed within the workpiece surface. This means that theelectrode 34 must be moved quite quickly to compensate for the hiatus tomaintain the constant quickly. This quick movement is to be accomplishedby means of the motor which is what is commonly referred to as a torquemotor. Torque motors are capable of making extremely fast responseswhich is needed in this instance and such motors are also capable ofbeing operated either clockwise or counterclockwise which is required inthis situation.

The preselected voltage value is to be measured between the electrode 34and the workpiece by means of electrical contacts 108 and 110. At thetime the arc is struck, a high energy field is initially generatedacross the arc gap. This high energy initial field could be quitedamaging to the control system and therefore inclusion of the inductor112 and the capacitor 1 14 is to suppress this high energy initialfield.

The welding voltage is transmitted to an attenuator 116 and into anamplifier 118. The amplified voltage is then transmitted into a secondamplifier 120. The amplifier 120 compares the sensed voltage with areference voltage which is transmitted from a potentiometer 122. Thepotentiometer circuit includes a potentiometer 122, a capacitor 124,with each end of the potentiometer circuit being connected to theelectronics ground line 126. i

A variable resistor 128 is interposed about the second amplifier 120 andis to function as a deadband adjustment. Upon the sensed voltage beingcompared with the reference voltage, either a positive or a negativeerror voltage will result except for the unusual situation when thevoltages are exactly equal. It is desirable for this error voltage toexceed a certain level before such is transmitted to effect activationof the motor 70. Therefore, the deadband, represented byvariableresistor 1 28, is to be adjusted so as to make the error voltageineffective within a certain band or range.'In other words, if the errorvoltage, multiplied by the gain of amplifier 120 is less thanthe-breakover voltage of the diodes 130 or 132, no signal is transmittedto amplifier 134. If the voltage is sufficiently great enough to exceedthe breakover voltage of the diodes 130 or 132, either a positive or anegative signal from the amplifier 134 will be transmitted to amplifier136. If a positive signal is transmitted to the motor 70, the motor willbe driven clockwise. If a negative signal is transmitted from theamplifier 136, the motor 70 will be driven counterclockwise. The drivingof the motor 70 will either raise or lower the electrode 34 so as tobring the arc voltage to the level established by the reference voltagecreated by the potentiometer 122. As soon as the arc voltage is withinthe deadband which is produced by the variable resistor 128, the signalto drive the motor is cut off (by the zero signal of amplifier 134) andat the same time the braking circuit is activated which effectivelyshort circuits the motor 70.

It is desirable to employ a braking circuit in order to eliminatecontinued inertial movement of the motor 70 resulting in continuedinertial movement of the electrode 34. At the time the motor 70 is cutoff, it begins to act as a generator. It is known that stopping agenerator is readily accomplished by the placement of a large loadwithin the generator circuit. The greatest load which can be achieved isa short circuit which will bring the motor 78 to a stop within a fewmilliseconds and still within the deadband range. The braking circuitincluded within the structure of this invention is designed to provide ashort circuit only when no signal is produced by amplifier 134.

Let it be assumed that a positive signal is being transmitted from theamplifier 134 with such signal also being transmitted through diode 138which in turn activates transistors 140 and 142. Upon this positivesignal going to zero, transistors 140 and 142 are turned off whichpermits the generated potential of the motor 70 to be transmittedthrough diode 144 to ground line 126. In essence, a short circuit hasoccurred.

Upon a negative signal being transmitted from the amplifier 134, saidsignal is transmitted through diode 146 and activates transistors 148and 150. Upon the signal from the amplifier 134 becoming zero, thetransistors 148 and 150 are deactivated. As a result, the generatedvoltage from the motor 70 is transmitted through the transistor 150 andthe diode 152 to in essence short circuit the motor 70.

If for some reason the workpiece was removed or displaced from theelectrode 34 a substantial distance, it would still be possible, ifsomeone activated the welding power source 154, to cause the arc tostrike at the electrode 34. This striking of the arc may be dangerousand could cause injury or damage. Therefore, if the workpiece has beenremoved, it is desirable to prevent such an arc being struck.

To prevent the are from striking, a safety circuit is provided whichincludes the use of a power source 156 which supplies the small currentacross resistor 158 located within the electronics ground line 126. Thewelding ground line 160 is connected through line 162 to the electronicsground line 126. The slight potential from the power source 156 isdesigned to be normally absorbed by resistor 158 and the resistor 154.

However, if the ground connection 160 is now lost, a potential existsbetween ground connections 126 and 160. This potential effectsactivation of transistor 166 which results in the activation of a relay168. The relay 168 then causes the normally closed contact 170 to open.With the contact 170 in the open position, it is not possible toactivate the welding power source 154 and the striking of the arc aboutthe electrode 34.

Referring particularly to FIGS. 4, and 8 to 14 of the drawings, theelectrode oscillating mechanism incorporated within this invention isdepicted. Motor 172 is fixedly mounted within the apparatus housing 22which is to be operated by a power source, not shown. The motor 172effects rotation of a drive shaft 174 which in turn is fixedly securedto a first clutch plate 176.

Located directly adjacent the first clutch plate 174 and shown spacedtherefrom in FIG. 4 of the drawings is a second clutch plate 178. Thesecond clutch plate 178 is connected through clutch mechanism 180 to adrive shaft 182. The clutch mechanism 180 is deemed to be conventionaland includes a magnetic biasing means which is to be activatedelectically. The clutch mechanism 180, as depicted in FIG. 4, shows suchto be inactivated with the clutch plates 176 and 178 spaced from eachother and not in engagement. Upon activation of the clutch mechanism180, the biasing means located within the mechanism 180 causes plate 178to move into frictional engagement with the plate 176.

A drive wheel 184 is fixedly secured upon the drive shaft 182. A bolt186 is engaged about the periphery of the drive wheel 184 with theopposite end of the belt 186 in engagement with a drive wheel 188. Thedrive wheel 188 is fixedly mounted upon an operating shaft 190. Shaft190 is rotatably mounted by hearing assemblies 192 and 194 within asleeve 196. The sleeve 196 is fixedly mounted by means of set screws 198within the apparatus housing 22.

The free end of the operating shaft 190 is integrally connected to aplate 200. Eccentrically mounted with respect to the operating shaft 190and located on the opposite side of the plate 200 is a pin 202. Pin 202is to rotationally cooperate with an external gear 204. The pin 202cooperates with an aperture centrally located within the gear 204.

An internal ring gear 206 is located about the external gear 204 andfits within appropriate recess means within the apparatus housing 22.The eccentric location of pin 202 is such so that the external gear 204is in continuous contact with the internal gear 206. The internal gear206 is pivotally mounted with respect to the apparatus housing 22 withsuch pivoting action being caused manually by means of handle 208 whichis screw threadingly attached within threaded opening 210 within theinternal gear 206. The threaded portion of the handle 208 passes throughan opening 212 within the apparatus housing 22 in order to communicatewith the opening 210. The sides of the opening 212 function as stops forlimiting the amount of pivotal movement of the internal gear 206. It isto be noted that the amount of pivotal movement of the interal gear 206is to be limited to the reason for such which will become apparentfurther on in the description.

A plate 214 is connected to the external gear 204 and on its undersidethereof includes a pin 216. Pin 216 is rotatably mounted by means ofbearing 218 to an actuating arm 220. The actuating arm 220 is locatedwithin a chamber 222 formed within a brake block 224. A slot 226 isformed within a side of the brake block 224 in order to permit theactuating arm 220 to extend exteriorly therefrom. The brake block 224 isconfined within a cylindrical recess formed within the apparatus housing22.

The brake block 224 includes an opening 228 within which a guide pin 230is located. The guide pin 230 is capable of a limited amount of movementwithin the opening 228 with the pin 230 being fixed within fixed block232. The fixed block 232 is fixedly located to the apparatus housing 22by means of screw fastener 234. A threaded opening 236 is centrallylocated within the fixed block 232. A threaded bolt 238 threadinglycooperates with the opening 236. The head of the bolt 238 is fixedlymounted within an opening 240 within a handle 242. The bolt 238 is fixedwithin-the handle 242 by means of fastener 244. The free end of the bolt230 is to be in continuous contact with the underside of the guide block232. A snap ring 246 cooperates at the underside of the fixed block 232within recess means formed within the fixed housing 22.

The free end of the actuating arm 220 is pivotally connected toextension 248 of the guide block 86. A cover 250 is secured to the fixedhousing 22 and is to protect the actuating arm 220 and its connectionsfrom being contaminated from foreign material.

The operation of the oscillating apparatus employed within thisinvention is as follows: Assuming that the clutch plates 176 and 178 arein frictional contact with each other, upon operation of motor 172rotation of drive wheel 184 occurs which results in rotation of drivewheel 188 through belt 186. As a result, operating shaft 190 is rotatedwhich results in a circular path movement of pin 202. This circular pathof movement also results in rotation of external gear 204 about theinternal gear 206. This in turn causes the pin 216 to move in a certainpath.

Referring particularly to FIGS. 9 to 14 of the drawings, the pin 216 isrepresented in dotted lines as the center of one end of the actuatingarm 220. The path of movement of this pin 216 is represented by thearrow 252 within the series of FIGS. 9 to 1 1. The same pin 216 and itspath of movement is also represented by arrow 254 within FIGS. 12 to l4.It is readily apparent that the path of movement of FIGS. 12 to 14 isdifferent than that of FIGS. 9 to 11 by reason of the pivotal movementof the internal gear 206 to a different position.

As the operating shaft 190 is rotated, the external gear 204 moves in acircle aboutthe center axis of the operating shaft 190. However, theexternal gear 204 itself rotates which causes the pin 216 and itsconnected end of the actuating arm 220 to move in a certain path. Thispath, due to the proper selection of the eccentricity of the pin 202,the size of the external gear 204, the size of the internal gear 206 andthe location of the pin 216, results in a linear path of the pin 216 atall times. This linear path can assume various angular positions butwill remain linear.

Within FIGS. 9 to 11 it is to be noted that the linear path, representedby arrow 252, is substantially transverse to the elongated actuating arm220. Therefore, as the operating shaft 190 is rotated, the operating endof the actuating arm 220 is moved back and forth in a transverse mannerwith only a pivoting action of the connecting end of the actuating armoccurring with respect to the extension 248. As a result, the guideblock 86 does not pivot with respect to the fixed housing but staysstationary. Since such is stationary, the electrode 34 does notoscillate transversely. Thissetting, which is to be preselected by thelocation of the internal gear 206 by means of manually moving handle208, is to be employed when a very small weld is to be produced, usuallybetween rather smaller diametered workpieces.

Within FIGS. 12 to 14 the handle 208 is shown pivoted approximately fromthe position of FIGS. 9 to 11. It is to be understood that the handle208 can further be pivoted to a position approximately 90 from thatshown within FIGS. 9 to 11. At this 90 position the maximum amplitude ofthe oscillating movement would occur.

Because, of the pivoting of the internal gear 206 with respect to theexternal gear 204 within FIGS. 12 to 14, the path of the pin 216represented by the arrow 254 is canted approximately 30 with respect tothe arrow 252. As a result, not only does the actuating arm 220 movetransversely, but also a movement component in the elongated directionof the actuating arm 220 occurs. This results in an oscillatory or backand forth motion of the extension 248. This oscillatory movement of theextension 248 is transferred into pivotal motion of the guide block 86by being pivoted about guide rod 90. As a result, an oscillating arcuatepath,

represented by arrow 256 occurs with the electrode 234. This oscillatorymovement will have been preselected in view of the width of the weldbead 32 which is to be produced. Normally this selection will be such sothat the electrode 34 will be moved adjacent the edges of the weld bead32 during its oscillatory movement.

As previously mentioned, it is tobe understood, that compared to FIGS.12 to 14, a greater'amplitude of the oscillatory movement can beachieved by further pivotal action of the internal gear 206 by manuallymoving such by means of handle 208. However, upon the ninety degreeposition being achieved as previously mentioned, the maximum amplitudeof the oscillatory movement will then be achieved with no transversecomponent but only a longitudinal movement component resulting. Normallythis maximum amplitude will not exceed 1% to 2 inches.

Upon the pivotal movement of the internal gear 206 being established, itis desired to maintain the position of the internal gear and not permitsuch to vary. There fore, the use of the brake block 224 is employed.

Upon the desired position of the internal gear 206 being established,the operator then manually pivots the handle 242 in a tighteningdirection. As a result, the bolt 228 is moved relative to the fixedblock 232 and likewise effects a movement of the brake block 224. Theperipheral edge of the upper surface of the brake block 224 locatedadjacent chamber 222 is caused to come into frictional engagement withthe internal gear 206. This frictional engagement forces the internalgear at its upper surface thereof into frictional engagement with thefixed housing 22. The depth of the chamber 222 is selected so as to nothinder the movement of the actuating arm 214 within the chamber 222. Asa result, the preselected position of the internal gear 206 isfrictionally held and accidental removal thereof is prevented.

When it is desired to change the amplitude of the oscillatory movement,it is only necessary to effect a quick untightening movement of thehandle 242 which releases the brake block 224. which likewise releasesthe internal gear 206. Therefore, ease is caused of pivotal movement ofthe internal gear 206 by means of handle 208. i

In the producing of significant width weld beads 32, normal continuousback and forth oscillatry movement tends to produce a weld bead with ahigh center. Therefore, it is desirable to fill in the edges of the weldbead. In order to fill in the edges, it is required that the weldingelectrode pause or dwell adjacent the edge of the weld head to result inthe depositing of an additional amount of the filler wire 38. Theapparatus to effect the dwelling of the electrode 34 will be describedas follows:

It is necessary that the apparatus to effect the dwelling be moved insynchronism with the apparatus to effect the oscillatory movement. Inorder to do this, a drive wheel 258 is employed which has the samenumber of teeth and is the same size as the drive wheel 188 which isresponsible for the producing of the oscillatory motion. The drive wheel258 is also driven by belt 186 and is rotatably mounted upon the fixedhousing 22. The drive wheel 258 is to be in continuous engagement withthe belt 186 as the drive wheel 188 is also in continuous engagementtherewith. The drive wheel 258 is rotatably supported with respect tothe apparatus housing 22 by means of bolt 260. A bearing assembly 262 islocated between the bolt 260 and the drive wheel Formed within theapparatus housing 22 is a recess 264. A bracket 266 is fixedly mountedto the apparatus housing 22 within the recess 264 by means of screwfastener 268. The configuration of the bracket 266 is basicallybifurcated having a cut-out section 270 located between legs 272 and274. Fixedly mounted within leg 270 is a light source 276. Light source276 is to be supplied electrical energy from a power supply, not shown.Located within the leg 272 is a first photocell 278 and a secondphotocell 280. It is to be understood for the purpose of descriptionthat the photocells 278 and 280 and the light source 276 have beenenlarged for illustrative purposes.

Located within the drive wheel 258 are a pair of apertures 282 and 284.The apertures 282 and 284 are diametrically located opposite each otherwith respect to the center of the drive wheel 258. However, aperture 282is located at a further radially outward distance from-the center of thedrive wheel 258 than aperture 284. The arrangement of the apertures 282and 284 is such so that during a single complete 360 revolution of thedrive wheel 258, aperture 282 at one point will permit of light from thelight source 276 to activate photocell 280. Also, during a single 360revolution of the drive wheel 258, at one point the aperture 284 will belocated so that light from the light source 276 will pass therethroughinto photocell 278. The previous arrangement is shown in FIG. 6 of thedrawings with the latter arrangement shown in FIG. 7 of the drawings.

The position of the drive wheel 258 is such with respect to the drivewheel 188 so that upon the light from the light source 276 passingthrough the aperture 282 and into the photocell 280, the electrode 34 islocated at one point of maximum displacement in its oscillatory movementpath. At that position it is desired to effect a dwell, which is causedby activation of the clutch mechanism 180 and disengagement of theclutch plates 176 and 178. Referring particularly to FIG. of thedrawings, this engagement procedure can be described in more detail.

Upon the photocell 280 being activated, a signal is transmitted toamplifier 286. The amplified signal is then transmitted to activate arelay 288. The relay 288 upon being activated, opens normally closedcontact 290, closes normally open contact 292 and opens normally closedcontact 294. Contact 294 upon being opened causes activation of themagnetic clutch mechanism 180. As a result, frictional clutch engagingplates 176 and 178 are caused to be spaced from each other resulting indisengagement of the clutch and a stopping of the movement of thewelding electrode 34.

At the same time the clutch mechanism 180 is activated, a timer 296 isactivated by the closing of the contact 292, The construction of thetimer is not specifically shown but is deemed to be conventional withsuch electronic timer mechanisms being commercially available fromseveral sources. Basically, the timer structure can be preselected toproduce a dwell for a period of time between l/lO to 2 seconds. At theend of the timed dwell period, the timer mechanism 296 is to transmit asignal directly to the clutch mechanism 180 and effect an overriding ofthe previous signal and effect engagement of the clutch plates 176 and178. Also along with the activation of contacts 292 and 294,

a contact 290 is activated which is located within the circuitry whichwould be activated by photocell 278. The opening of contact 290 therebyprohibits inadvertent activation of the opposite circuit which mightcause an increase in dwell time.

Upon the timer mechanism 296 having been reactivated, the clutchmechanism and the drive wheels 184 are again driven as well as the wheel258. Upon the wheel 258 being slightly-rotated, the light source is nolonger capable of passing through aperture 282 and into contact withphotocell 280. Therefore, photocell 280 becomes inactive resulting in nosignal being transmitted to amplifier 286 which results in deactivationof relay 288. This deactivation of relay 288 results in contact 290returning to the closed position, contact 292 returning to the openposition and contact 294 returning to the closed position which placesall components back in the original position.

Upon 180 movement of the drive wheel 258, the aperture 284 becomeslocated between the light source 276 and the photocell 278. Uponactivation of photocell 278, a similar occurrence occurs with respect tothe previous arrangement with the signal being transmitted fromamplifier 286 to relay 298. With the relay 298 being activated, normallyclosed contact 300 is open with normally open contact 302 closed andnormally closed contact 304 opened. In a similar manner the clutchmechanism 180 is then deactivated which results in disengagement of theplates 176 and 178 resulting in a dwell being produced. At the same timeby the closing of contact 302 the timer mechanism 296 is activated for aparticularly selected dwell time.

It is to be understood that the timer mechanism 296 is to normallyinclude two timing circuits so that separate dwell times can beestablished for the opposite sides of the maximum displacement point ofthe oscillating movement path. At the same time contact 300 is openwhich is located within the circuit path which is activated by photocell280 to insure that circuit path cannot be inadvertently activated.

Referring particularly to FIG. 16 of the drawings, a more detailedelectrical diagram is shown of the block diagram arrangement shown inFIG. 15 of the drawings. Upon the photocell 280 being activated, asignal is caused to activate transistor 306. By activation of transistor306, a signal is transmitted to transistor 308 which results in acurrent flow through diode 310 to activate relay 288. The relay 288 isalso interconnected to contact 290 which is simultaneously opened. Uponthe photocell 280 being deactivated, transistors 306 and 308 aredeactivated which results in deactivation of relay 288 which results ina reclosing of contact 290.

Upon photocell'278 being activated, a signal is transmitted totransistors 312 and 314 in a similar manner. The signal from thetransistor 314 is transmitted through diode 316 to activate relay 298.Upon activation of relay 298, clutch mechanism 180 is activated todisengage the clutch plates 176 and 178 as in a similar manner the timermechanism 296 is activated with contact 300 being opened. Upondeactivation of the photocell 278, the transistors 312, 314 and therelay 298 are deactivated with the result that contact 300 as well ascontacts 302 and 304 are returned to their original positions.

We claim:

1. An apparatus for producing oscillatory movement transverse to thelongitudinal path of movement of a welding electrode comprising:

support means for retaining said electrode;

actuating means connected to said support means, said actuating meansincluding means for causing movement of said support means to result intransverse oscillatory movement of said electrode;

movement producing means connected through a driving means to saidactuating means;

dwell producing means for causing a dwell in said oscillatory movementat a point of maximum displacement of said electrode;

a motor assembly connected to said movement producing means, said motorassembly to operate said actuating means through said driving means; and

said dwell producing means includes a photocell sensing arrangementwhich is connected to said motor assembly, said photocell sensingarrangement is connected to control means to effect nontransmitting ofthe torque of said motor assembly to said actuating means.

2. An apparatus as defined in claim 1 wherein:

said control means includes a clutch, said clutch connected between saidmotor assembly and said actuating means, said photocell sensingarrangement capable of disengaging said clutch thereby producing saiddwell.

3. Apparatus as defined in claim 2 wherein:

said control means of said dwell producing means including a timerassembly to control the length of dwell time, said timer assemblyconnected to said clutch, upon disengaging of said clutch said timerassembly being engaged, said timer assembly operates reengagement meansto effect reengagement of said clutch after expiration of the dwell timeestablished by said timer assembly.

4. Apparatus as defined in claim 3 wherein:

said photocell sensing arrangement includes a first photocell and asecond photocell, a light source, blocking means located between saidlight source and said first and second photocells to normally preventlight from being transmitted from said light source to said photocells,aperture means located within said blocking means, said aperture meansto permit transmission of light from said light source to either of saidphotocells which activates said control means, said first photocell tocontrol dwell of said electrode at one side of the electrode path withsaid second photocell to control dwell at the opposite side of theelectrode path.

5. Apparatus as defined in claim 4 wherein:

said timer assembly comprises a first timer operated through means bysaid first photocell and a second timer operated through means by saidsecond photocell.

6. Apparatus as defined in claim 4 wherein:

said blocking means comprises a rotating disc, said disc connectedthrough means to said electrode, a complete rotation of said disc to besynchronous to a complete cycle of said oscillatory movement, saidaperture means includes a pair of apertures diametrically located uponsaid disc, the radial spacing of said apertures upon said disc beingdifferent, only one of said apertures permitting light transmissionbetween said light source and said first photocell during a completerevolution of said disc with only the other of said apertures permittinglight transmission between said light source and said second photocellduring a complete revolution of said disc.

7. An apparatus for producing oscillatory movement transverse to thelongitudinal path of movement of a welding electrode comprising:

support means for retaining said electrode;

actuating means connected to said support means, said actuating meansincluding means for causing movement of said support means to result intransverse oscillatory movement of said electrode;

movement producing means connected through a driving means to saidactuating means;

dwell producing means for causing a dwell in said oscillatory movementat a point of maximum displacement of said electrode;

said movement producing means includes an external gear, an internalgear located about said external gear and in continuous engagementtherewith, a motor assembly connected to said external gear, saidexternal gear attached to said driving means, whereby rotationalmovement of said external gear is capable of causing lineal movement ina given direction of said driving means.

8. Apparatus as defined in claim 7 wherein:

said internal gear mounted within a housing, said internal gear beingpivotal within said housing, a pin eccentrically mounted upon saidexternal gear, said pin connected to said driving means, said pinmovable substantially through a lineal path as said external gearrotates, pivoting of said internal gear also changes the position ofsaid external gear thereby changing the angular position of said linealpath to said given direction of said driving means to thereby change theamplitude of said oscillatory movement.

9. Apparatus as defined in claim 8 including:

lock means connected to said housing to fixedly position said internalgear at the established pivotable position.

10. Apparatus as defined in claim 8 including:

a motor assembly connected to said movement producingmeans, said motorassembly to operate said actuatingmeans through said driving means; and

said dwell producing means including a photocell sensing arrangementwhich is connected to said motor assembly, said photocell sensingarrangement is connected to control means to effect nontransmitting ofthe torque of said motor assembly to said actuating means.

11. Apparatus as defined in claim 10 wherein:

said control means includes a clutch, said clutch connected betweensaidmotor assembly and said actuating means, said photocell sensingarrangement capable of disengaging said clutch thereby producing saiddwell.

12. An apparatus for producing transverse oscillatory movement of awelding electrode comprising:

support means for retaining said electrode;

actuating means connected to said support means, said actuating meanscapable of causing movement of said support means to result intransverse oscillatory movement of said electrode; and

movement producing means connected to said actuating means, saidmovement producing means including an external gear connected to saidactuating means, said external gear in continuous engagement with aninternal gear.

13. Apparatus as defined in claim 12 wherein:

said internal gear mounted within a housing, said internal gearpivotable within said housing to thereby change the amplitude of saidoscillatory movement.

14. Apparatus as defined in claim 13 wherein:

lock means connected to said housing to fixedly position said internalgear upon the pivotable position of such being established.

15. In an automatic welding apparatus having a welding electrode, saidwelding electrode to move longitudinally in a prescribed path to producea weld bead upon a workpiece, said apparatus including:

first means for causing transverse oscillatory movement of saidelectrodes;

second means for causing a dwelling in said oscillatory movement at apoint of maximum displacement a motor assembly connected to said firstmeans for supplying input power to said first means; and

said second means includes a photocell sensing arrangement which isconnected to said motor assembly, said photocell sensing arrangement isconnected to control means to effect non-transmitting of the torque ofsaid motor assembly to said first means.

16. Apparatus as defined in claim 15 wherein:

said control means includes a clutch, said clutch connected between saidmotor assembly andsaid first means, said photocell sensing arrangementcapable of disengaging said clutch thereby producing said dwelling ofsaid oscillatory movement.

17. Apparatus as defined in claim 16 wherein:

said control means of said second means including a timer assembly tocontrol the length of dwell time, said timer assembly connected to saidclutch, upon disengaging of said clutch said timer assembly beingengaged, said timer assembly operates reengagement means to effectreengagement of said clutch after expiration of the dwell time by saidtimer assembly.

18. Apparatus as defined in claim 17 wherein:

said photocell sensing arrangement includes a first photocell and asecond photocell, a light source, blocking means located between saidlight source and said first and second photocells to normally preventlight from being transmitted from said light source to said photocells,aperture means located within said blocking means, said aperture meansto permit transmission of light from said light source to either of saidphotocells which activates said control means, said first photocell tocontrol dwell of said electrode at one side of the electrode path withsaid second photocell to control the dwell at the opposite side of theelectrode path.

19. Apparatus as defined in claim 18 wherein:

said blocking means comprises a rotating disc, said disc connectedthrough means to said electrode, a complete rotation of said disc to besynchronous to a complete cycle of said oscillatory movement, saidaperture means includes a pair of apertures diametrically located uponsaid disc, the radial spacing of said apertures upon said disc beingdifferent, only one of said apertures permitting light transmissionbetween said light source and said first photocell during a completerevolution of said disc with only the other of said apertures permitinglight transmission between said light source and and said secondphotocell during a complete revolution of said disc.

1. An apparatus for producing oscillatory movement transverse to thelongitudinal path of movement of a welding electrode comprising: supportmeans for retaining said electrode; actuating means connected to saidsupport means, said actuating means including means for causing movementof said support means to result in transverse oscillatory movement ofsaid electrode; movement producing means connected through a drivingmeans to said actuating means; dwell producing means for causing a dwellin said oscillatory movement at a point of maximum displacement of saidelectrode; a motor assembly connected to said movement producing means,said motor assembly to operate said actuating means through said drivingmeans; and said dwell producing means includes a photocell sensingarrangement which is connected to said motor assembly, said photocellsensing arrangement is connected to control means to effectnon-transmitting of the torque of said motor assembly to said actuatingmeans.
 2. An apparatus as defined in claim 1 wherein: said control meansincludes a clutch, said clutch connected between said motor assembly andsaid actuating means, said photocell sensing arrangement capable ofdisengaging said clutch thereby producing said dwell.
 3. Apparatus asdefined in claim 2 wherein: said control means of said dwell producingmeans including a timer aSsembly to control the length of dwell time,said timer assembly connected to said clutch, upon disengaging of saidclutch said timer assembly being engaged, said timer assembly operatesreengagement means to effect reengagement of said clutch afterexpiration of the dwell time established by said timer assembly. 4.Apparatus as defined in claim 3 wherein: said photocell sensingarrangement includes a first photocell and a second photocell, a lightsource, blocking means located between said light source and said firstand second photocells to normally prevent light from being transmittedfrom said light source to said photocells, aperture means located withinsaid blocking means, said aperture means to permit transmission of lightfrom said light source to either of said photocells which activates saidcontrol means, said first photocell to control dwell of said electrodeat one side of the electrode path with said second photocell to controldwell at the opposite side of the electrode path.
 5. Apparatus asdefined in claim 4 wherein: said timer assembly comprises a first timeroperated through means by said first photocell and a second timeroperated through means by said second photocell.
 6. Apparatus as definedin claim 4 wherein: said blocking means comprises a rotating disc, saiddisc connected through means to said electrode, a complete rotation ofsaid disc to be synchronous to a complete cycle of said oscillatorymovement, said aperture means includes a pair of apertures diametricallylocated upon said disc, the radial spacing of said apertures upon saiddisc being different, only one of said apertures permitting lighttransmission between said light source and said first photocell during acomplete revolution of said disc with only the other of said aperturespermitting light transmission between said light source and said secondphotocell during a complete revolution of said disc.
 7. An apparatus forproducing oscillatory movement transverse to the longitudinal path ofmovement of a welding electrode comprising: support means for retainingsaid electrode; actuating means connected to said support means, saidactuating means including means for causing movement of said supportmeans to result in transverse oscillatory movement of said electrode;movement producing means connected through a driving means to saidactuating means; dwell producing means for causing a dwell in saidoscillatory movement at a point of maximum displacement of saidelectrode; said movement producing means includes an external gear, aninternal gear located about said external gear and in continuousengagement therewith, a motor assembly connected to said external gear,said external gear attached to said driving means, whereby rotationalmovement of said external gear is capable of causing lineal movement ina given direction of said driving means.
 8. Apparatus as defined inclaim 7 wherein: said internal gear mounted within a housing, saidinternal gear being pivotal within said housing, a pin eccentricallymounted upon said external gear, said pin connected to said drivingmeans, said pin movable substantially through a lineal path as saidexternal gear rotates, pivoting of said internal gear also changes theposition of said external gear thereby changing the angular position ofsaid lineal path to said given direction of said driving means tothereby change the amplitude of said oscillatory movement.
 9. Apparatusas defined in claim 8 including: lock means connected to said housing tofixedly position said internal gear at the established pivotableposition.
 10. Apparatus as defined in claim 8 including: a motorassembly connected to said movement producing means, said motor assemblyto operate said actuating means through said driving means; and saiddwell producing means including a photocell sensing arrangement which isconnected to said motor assembly, said photocell sensing arrangement isconnected to control means to effect non-transmitting of the torque ofsaid motor assembly to said actuating means.
 11. Apparatus as defined inclaim 10 wherein: said control means includes a clutch, said clutchconnected between said motor assembly and said actuating means, saidphotocell sensing arrangement capable of disengaging said clutch therebyproducing said dwell.
 12. An apparatus for producing transverseoscillatory movement of a welding electrode comprising: support meansfor retaining said electrode; actuating means connected to said supportmeans, said actuating means capable of causing movement of said supportmeans to result in transverse oscillatory movement of said electrode;and movement producing means connected to said actuating means, saidmovement producing means including an external gear connected to saidactuating means, said external gear in continuous engagement with aninternal gear.
 13. Apparatus as defined in claim 12 wherein: saidinternal gear mounted within a housing, said internal gear pivotablewithin said housing to thereby change the amplitude of said oscillatorymovement.
 14. Apparatus as defined in claim 13 wherein: lock meansconnected to said housing to fixedly position said internal gear uponthe pivotable position of such being established.
 15. In an automaticwelding apparatus having a welding electrode, said welding electrode tomove longitudinally in a prescribed path to produce a weld bead upon aworkpiece, said apparatus including: first means for causing transverseoscillatory movement of said electrodes; second means for causing adwelling in said oscillatory movement at a point of maximum displacementa motor assembly connected to said first means for supplying input powerto said first means; and said second means includes a photocell sensingarrangement which is connected to said motor assembly, said photocellsensing arrangement is connected to control means to effectnon-transmitting of the torque of said motor assembly to said firstmeans.
 16. Apparatus as defined in claim 15 wherein: said control meansincludes a clutch, said clutch connected between said motor assemblyandsaid first means, said photocell sensing arrangement capable ofdisengaging said clutch thereby producing said dwelling of saidoscillatory movement.
 17. Apparatus as defined in claim 16 wherein: saidcontrol means of said second means including a timer assembly to controlthe length of dwell time, said timer assembly connected to said clutch,upon disengaging of said clutch said timer assembly being engaged, saidtimer assembly operates reengagement means to effect reengagement ofsaid clutch after expiration of the dwell time by said timer assembly.18. Apparatus as defined in claim 17 wherein: said photocell sensingarrangement includes a first photocell and a second photocell, a lightsource, blocking means located between said light source and said firstand second photocells to normally prevent light from being transmittedfrom said light source to said photocells, aperture means located withinsaid blocking means, said aperture means to permit transmission of lightfrom said light source to either of said photocells which activates saidcontrol means, said first photocell to control dwell of said electrodeat one side of the electrode path with said second photocell to controlthe dwell at the opposite side of the electrode path.
 19. Apparatus asdefined in claim 18 wherein: said blocking means comprises a rotatingdisc, said disc connected through means to said electrode, a completerotation of said disc to be synchronous to a complete cycle of saidoscillatory movement, said aperture means includes a pair of aperturesdiametrically located upon said disc, the radial spacing of saidapertures upon said disc being different, only one of said aperturespermitting light transmission between said light source and said firstphotocell during a complete revolution of said disc with only the otherof said apertures permiting light transmission between said light sourceand and said second photocell during a complete revolution of said disc.